Electronic mail, also commonly referred to as “email” or “e-mail”, is increasingly used as an electronic form of communication via the Internet. Email can be a useful and efficient way of communicating. Spam is unsolicited and/or undesirable email often sent to email distribution lists that include a large number of users' email addresses. Spam is similar to telemarketing and is the electronic equivalent of “junk mail” used to advertise products and services, request charitable donations, or to broadcast some political or social commentary. Spamming is the practice of sending an unsolicited email message to large numbers of email addresses. Such spam emails are often unwanted by the recipients, who may need to spend time a significant amount of time sorting through their email and deleting spam emails. In addition to consuming the recipient's time, such spam emails may interfere with the recipients normal email communications. Spam emails are also generally considered to be a waste of network bandwidth and can quickly fill-up file server storage space.